AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Development of a Portable Aerosol Collector and Spectrometer (PACS)
CAI CHANGJIE, Geb Thomas, Sivaram Gogineni, Tianbao Yang, Thomas Peters, University of Iowa
Abstract Number: 287 Working Group: Instrumentation and Methods
Abstract Objectives: Current portable instruments cannot continuously measure exposures to all particle size ranges and collect particles simultaneously. The aim of this study was to develop an instrument, the Portable Aerosol Collector and Spectrometer (PACS), to continuously measure particle size distributions by number, surface area and mass concentrations over a wide size range (from 10 nm to 10 µm), and to collect particles by size for post-processing chemical analyses.
Methods: We designed the PACS to direct aerosol from the breathing zone sequentially through a series of impactors and diffusion screens that separate particles into six bins by size. The number and mass concentration of the airborne particles exiting each bin are then measured with a water condensation particle counter and a photometer. The best-fit tri-modal, log-normal distribution is fit to this set of 12 measurements. In these experiments, we compared the number, surface area, and mass concentrations measured by the PACS for laboratory-generated fresh welding fume (nano-sized particles; ultrafine mode), aged welding fume (fine mode) and Arizona road dust (coarse mode) to that measured by a scanning mobility particle sizer (SMPS) and aerodynamic particle sizer (APS). The collected particles are then chemically analyzed to measure the particle size distributions of metal elements. In these experiments, we compared the mass concentrations of Fe and Cu collected by the PACS for laboratory-generated 3-mode aerosol to that collected by a reference cascade impactor (Nano-MOUDI). The percentage bias was calculated based on the measurements from the PACS compared to the measurements from the Nano-MOUDI. The correlation coefficient (r) was calculated based on fitting and reference particle size distributions for each metal element.
Results: In this study, by comparing to the SMPS/APS, for number concentration, the percentage bias was -3% coupled with an r of 0.98; for surface area, the percentage bias was 26% coupled with r of 0.67; for mass concentration, the percentage bias was -34% coupled with r of 0.9. By comparing to the Nano-MOUDI, for Fe element, the percentage bias was -20% coupled with an r of 0.93; for Cu element, the percentage bias was -1% coupled with R of 0.84. Moreover, we were able to use the elemental data to distinguish aerosols in different size modes. Therefore, the particle size distributions estimated with the PACS agreed reasonably well with those measured with the reference instrument.
Conclusions: Particle size distributions in various metrics (number, surface area and mass concentrations) measured by the PACS agreed reasonably well with those measured by reference instruments. This work also demonstrates that the PACS allows portable measurement of particle size distributions of the metals in ultrafine, fine, and coarse mode aerosols.